Small Craft Advisory 949, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
404 PM AKST SAT NOV 28 2015

.ANALYSIS AND UPPER LEVELS...
THE BROAD LONGWAVE TROUGH ANCHORED OVER THE NORTHWEST BERING SEA
AND EXTENDING ACROSS THE ALASKA PENINSULA INTO THE GULF OF ALASKA
CONTINUES TO BE THE DOMINANT FORCE FOR THE WEATHER.

THE REMAINS OF THE LOW THAT WAS IN BRISTOL BAY YESTERDAY ARE NOW
OVER THE NUNIVAK ISLAND AREA. THESE ARE PRODUCING WEAK ONSHORE
FLOW OVER BRISTOL BAY AND THE KUSKOKWIM DELTA THAT HAS BROUGHT
SOME LOCALLY DENSE FOG TO A FEW COASTAL LOCATIONS TODAY. COLDER
AIR IS WRAPPING AROUND THIS LOW RESULTING IN MORE CONVECTIVE
SHOWERY CONDITIONS. WITH THE EXPECTED LOW LEVEL COOLING TONIGHT WE
WILL MOST LIKELY SEE AREAS OF FOG OVER SOUTHWEST ALASKA OVERNIGHT.

A LARGE LOW NOW SOUTH OF SHEMYA HAS A FRONT EXTENDING IN AN ARC
INTO THE WESTERN BERING SEA THEN SOUTHEAST THROUGH THE CENTRAL
ALEUTIANS. SCATTEROMETER WINDS SHOW GALE FORCE WINDS ARE IN
ADVANCE OF THIS LOW AND FRONT AND A SMALL AREA OF STORM FORCE
WESTERLY WIND IS ON THE SOUTHWEST QUADRANT OF THIS LOW.

A WEAK FRONT HAS PUSHED INLAND ALONG THE NORTH GULF COAST FOLLOWED
BY A RIDGE BUILDING IN BEHIND IT. THIS IS CREATING THE PUSH FOR
THE GUSTY SOUTH AND SOUTHEAST WINDS THROUGH THE GAPS IN THE
CHUGACH MOUNTAINS. THIS SHOULD BE SHORT LIVED AS THE RIDGING
WEAKENS AND THE LOW OVER THE SOUTHWEST END OF KODIAK ISLAND
CONTINUES TO MOVE EAST AND ALSO WEAKEN TONIGHT.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN VERY GOOD AGREEMENT INTO EARLY NEXT WEEK WITH
RESPECT TO THE OVERALL SYNOPTIC PATTERN. WE WILL THEREFORE
CONTINUE TO USE THE HIGHER RESOLUTION MODELS FOR THE BETTER DETAIL
IN THE FORECAST PROCESS TO HANDLE THE GAP WINDS AND PRECIPITATION
FIELDS OVER THE SOUTHERN MAINLAND. THE MODELS ARE IN RELATIVELY
GOOD AGREEMENT WITH THE LOW MOVING ALONG THE ALEUTIAN CHAIN
THROUGH SUN NIGHT AND MONDAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

AN UNSETTLED WEATHER REGIME WILL CONTINUE THROUGH THE BEGINNING OF
THE UPCOMING WEEK AS SOUTHERLY FLOW ALOFT CONTINUES TO ADVECT
MOISTURE NORTH ACROSS SOUTHCENTRAL ALASKA. PRECIPITATION WILL BE
LARGELY CONFINED TO COASTAL AND UP-SLOPE LOCATIONS WITH JUST
ENOUGH CROSS BARRIER FLOW TO KEEP LEEWARD LOCATIONS (LIKE
ANCHORAGE AND KENAI) ON THE DRY SIDE. AN ISOLATED SHOWER OR TWO
WILL BE POSSIBLE INLAND THROUGH SUNDAY AFTERNOON AS THE UPPER
LEVEL TROUGH PUSHES ACROSS THE REGION. TEMPERATURES WILL CONTINUE
TO REMAIN WELL ABOVE NORMAL BUT A GRADUAL COOLING TREND IS
EXPECTED OVER THE COMING DAYS AS 500 MB HEIGHTS BEGIN TO DROP. 850
MB TEMPERATURES WILL REMAIN IN THE -2 TO -4 DEGREES CELSIUS RANGE
WHICH WILL LIKELY LEAD TO SOME PRETTY DECENT INVERSIONS DEVELOPING
ACROSS INLAND AREAS WHICH MAY LEAD TO PATCHY FOG DURING THE
OVERNIGHT HOURS STARTING TONIGHT. A FRONT WILL PUSH INTO THE
WESTERN GULF OF ALASKA LATE SUNDAY/EARLY MONDAY AND INCREASE
PRECIPITATION CHANCES ACROSS KODIAK ISLAND AND THE NORTHERN GULF
COAST WHILE INLAND LOCATIONS WILL REMAIN LARGELY ON THE DRY SIDE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
LIGHT WINDS ARE EXPECTED TONIGHT AS A WEAK SURFACE TROUGH PERSISTS
ACROSS THE SOUTHWEST MAINLAND. THIS COUPLED WITH A SATURATED AIR
MASS AND A WEAK INVERSION JUST OFF THE SURFACE WILL BRING AREAS OF
FOG ACROSS BRISTOL BAY AND PATCHY FOG TO THE KUSKOKWIM. A WARM
FRONT MOVES INTO THE THE ALASKA PENINSULA EARLY SUNDAY BRINGING
RAIN AND GUSTY WINDS. THIS FRONT MOVES INTO THE THE SOUTHWEST
SUNDAY NIGHT SPREADING PRECIPITATION NORTH TO BRISTOL BAY AND THE
KUSKOKWIM. ON MONDAY WINDS BECOME EAST AS THE FRONT MOVES IN WITH
GUSTY CONDITIONS ACROSS THE WESTERN CAPES AND ALEUTIAN RANGE. ONLY
MINOR RAIN AND SNOW ACCUMULATIONS ARE EXPECTED AS THE STACKED LOW
STAYS TO THE SOUTH OF THE ALASKA PENINSULA THROUGH MONDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
LOW PRESSURE PUSHES A FRONT INTO THE WESTERN ALEUTIANS THIS
EVENING THAT MOVES QUICKLY TO THE EASTERN ALEUTIANS ON SUNDAY
BEFORE SLOWING DOWN AS IT SLIDES JUST SOUTH OF THE ALASKA
PENINSULA MONDAY. SNOW AND RAIN WILL ACCOMPANY THE FRONT ALONG
WITH GUSTY GALE WINDS ALONG THE ALEUTIAN CHAIN. WINDS BECOME
NORTHWESTERLY BEHIND THIS SYSTEM AND ADVECT COLDER AIR BACK INTO
THE BERING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

BEGINNING THE EXTENDED PERIOD ON MONDAY EVENING...A BROAD UPPER
LOW CENTERED OVER THE EASTERN BERING AND NORTH PACIFIC WILL
ENCOMPASS THE ENTIRE REGION AS THE NORTH PACIFIC JET REMAINS
CENTERED IN THE VICINITY OF 40N. A SECONDARY LOW IN THE VICINITY
OF THE ALASKA PANHANDLE WILL ROTATE WEST INTO THE NORTHERN
GULF...SPREADING RAIN AND SNOW ALONG THE GULF OF ALASKA COAST.
INLAND LOCATIONS WILL REMAIN UNDER THE INFLUENCE OF MODERATE EAST
TO SOUTHEAST FLOW...WITH THIS DOWNSLOPE SHADOW KEEPING
PRECIPITATION MAINLY CONFINED TO COASTAL AND MARINE LOCATIONS.
FARTHER WEST...THE BULK OF COLD ARCTIC AIR WILL REMAIN OVER THE
WESTERN AND CENTRAL BERING SEA...WITH EXTENSIVE INSTABILITY
SHOWERS AND STRONG NORTHWEST WINDS. WITH AN ARCTIC HIGH CENTERED
NORTH OF THE NORTH SLOPE OF ALASKA...COLDER SURFACE LEVEL AIR WILL
INFILTRATE SOUTHERN ALASKA...ALLOWING TEMPERATURES TO MODERATE AND
COOL BACK TO NEAR NORMAL HEADING INTO THE LATE WEEK. ANOTHER NORTH
PACIFIC LOW WILL MERGE WITH THE ARCTIC TROUGH LATE
WEEK...DEEPENING INTO A DEEP LOW SOMEWHERE ACROSS THE SOUTHERN AND
EASTERN GULF OF ALASKA. MUCH UNCERTAINTY ARISES BY THIS
POINT...BUT SOME GUIDANCE DRIVES IN A STRONG STORM FORCE LOW
THROUGH THE GULF OF ALASKA LATE FRIDAY INTO SATURDAY...BUT THERE
REMAINS TOO MUCH UNCERTAINTY WITH TRACK AND POSITION TO REALLY GET
EXCITED AT THIS JUNCTURE. EITHER WAY...THE GENERAL PATTERN OF COLD
AIR OVER THE BERING AND STRONG EASTERLY LOW TO MID LEVEL FLOW OVER
SOUTHERN ALASKA WILL KEEP PRECIPITATION LARGELY RELEGATED TO
COASTAL LOCALES...WITH NO DRAMATIC CHANGE IN THE SENSIBLE WEATHER
INLAND. HEADING THROUGH THE WEEKEND...THE NORTH PACIFIC JET STREAM
WILL MOVE EAST...WITH STORMINESS CONTINUING TO IMPACT THE
PANHANDLE OF ALASKA AS SOUTHERN ALASKA REMAINS UNDER THE INFLUENCE
OF WEAKER LOWS DYING IN THE GULF OF ALASKA. IN OTHER WORDS...NO
SIGNIFICANT INLAND STORMS ARE EXPECTED THROUGH THE EXTENDED
PERIOD...WITH NEAR NORMAL TEMPERATURES.

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 132 150 173-176 178.

&&

SYNOPSIS AND MODEL DISCUSSION...SAM
SOUTHCENTRAL ALASKA...MC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...JA